A rapid, noninvasive and highly reliable method for the early diagnosis of Pneumocystis carinii (PC) pneumonitis in patients with the acquired immunodeficiency syndrome (AIDS) is urgently needed. A counterimmunoelectrophoresis (CIE) test for PC antigenemia has met these criteria and can detect antigen during the subclinical prodrome. It is therefore proposed that our facility serve as a national testing site for sera from AIDS and other cancer and immunocompromised patients. CIE tests will be conducted in parallel with the newly developed quantitative latex particle agglutination (LPA) test for PC antigen titering that employs monoclonal antibody prepared vs. cell culture-grown organisms. Antigen test data on all patients in the continental U.S. sent by overnight air express will be available within 6 hrs. of specimen receipt. Antibody titers will be determined by indirect immunofluorescence (IFA) and the newly developed enzyme-linked immunospecific assay (ELISA) using cell culture-grown PC as antigen. These tests have potential for decreasing morbidity and mortality from PC and providing a means for monitoring response to therapy, defining "at risk" patients with subacute PC, determining who should be subjected to invasive diagnostic methods, which patients should be "crossed over" to pentamidine, and for assessing prognosis. In essence, it will provide rapid simultaneous PC antigen and antibody titers on patients and their contacts, thus offering a unique opportunity to serologically monitor PC in AIDS and non-AIDS patients with malignancy. Quantitative antigen titers via monoclonal antibody to Pneumocystis carinii linked to latex beads should provide a means for defining length of prodrome, and how antigen titer correlates with clinical course and antibody response. A study of this nature, would provide the first in-depth serologic profile of AIDS patients. Other individuals potentially benefiting from this work include those with hematologic malignancies and solid tumors, chronic debilitating disease and compromised immunity due to necessary chemotherapy and radiation, immaturity, starvation, autoimmune disease, rheumatologic disorder and inborn immunodeficiency. In summary, the planned studies offer a unique opportunity to standardize Pneumocystis carinii antigen/antibody testing and to gather valuable data that will find immediate application in the management of Pneumocystis carinii pneumonia in cancer patients.